This invention relates to an improved method of making a magnetic gap, and more particularly relates to an improved method of making a magnetic head having excellent electromagnetic conversion characteristics.
A magnetic gap has been used widely for making magnetic heads for recording and reproducing video signals and sound signals. In production of the magnetic gap, a non-magnetic spacer for the operative gap has been formed from glass material. There are several methods known for making such a glass gap. For instance, a magnetic head core material is first immersed in a mixed solution of finely-crushed glass, than taken out and subjected to centrifugation so that a homogeneous layer of said pulverized glass is deposited on the opposing gap surfaces of the core menbers. After forming a glass film on said core surfaces by firing the thus deposited glass layer, the two opposing gap faces are butted against each other with said glass film sandwiched therebetween and fused together by a heat treatment to form the desired operative gap. These methods for making a magnetic gap according to the prior art have disadvantages such that they are difficult to use in the production of magnetic gaps with high precision because of difficulty in controlling the film thickness of the fired glass.
Cathode sputtering has been proposed as another method for depositing said glass films in order to produce the magnetic head gap. At present, however, it is quite doubtful that a conventional cathode sputtering technique can provide magnetic head gaps with high accuracy. The reasons are that (i) the magnetic core materials such as Mn-Zn ferrite are often damaged by the of plasma radiation during the sputtering deposition; (ii) the thickness accuracy of deposited films obtained in a conventional sputtering apparatus is around 10 to 20% when operating at a production scale, and higher accuracy is necessary for making said magnetic head gaps; (iii) reliable techniques for directly monitoring the thickness of the sputtered glass layer on the magnetic core materials are not well established, because the well-known quartz thickness monitor system is not adaptable for the direct monitoring of the glass layer thickness during sputtering deposition.
This invention relates to major improvements in the method of making the magnetic head gaps by cathodic sputtering.